/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.core.type.classreading;

import org.springframework.core.io.DefaultResourceLoader;
import org.springframework.core.io.Resource;
import org.springframework.core.io.ResourceLoader;
import org.springframework.lang.Nullable;
import org.springframework.util.ClassUtils;

import java.io.FileNotFoundException;
import java.io.IOException;

/**
 * Simple implementation of the {@link MetadataReaderFactory} interface,
 * creating a new ASM {@link org.springframework.asm.ClassReader} for every request.
 *
 * @author Juergen Hoeller
 * @since 2.5
 */
public class SimpleMetadataReaderFactory implements MetadataReaderFactory
{

    private final ResourceLoader resourceLoader;


    /**
     * Create a new SimpleMetadataReaderFactory for the default class loader.
     */
    public SimpleMetadataReaderFactory()
    {
        this.resourceLoader = new DefaultResourceLoader();
    }

    /**
     * Create a new SimpleMetadataReaderFactory for the given resource loader.
     *
     * @param resourceLoader the Spring ResourceLoader to use
     *                       (also determines the ClassLoader to use)
     */
    public SimpleMetadataReaderFactory(@Nullable ResourceLoader resourceLoader)
    {
        this.resourceLoader = (resourceLoader != null ? resourceLoader : new DefaultResourceLoader());
    }

    /**
     * Create a new SimpleMetadataReaderFactory for the given class loader.
     *
     * @param classLoader the ClassLoader to use
     */
    public SimpleMetadataReaderFactory(@Nullable ClassLoader classLoader)
    {
        this.resourceLoader = (classLoader != null ? new DefaultResourceLoader(classLoader) : new DefaultResourceLoader());
    }


    /**
     * Return the ResourceLoader that this MetadataReaderFactory has been
     * constructed with.
     */
    public final ResourceLoader getResourceLoader()
    {
        return this.resourceLoader;
    }


    @Override
    public MetadataReader getMetadataReader(String className) throws IOException
    {
        try
        {
            String resourcePath = ResourceLoader.CLASSPATH_URL_PREFIX + ClassUtils.convertClassNameToResourcePath(className) + ClassUtils.CLASS_FILE_SUFFIX;
            Resource resource = this.resourceLoader.getResource(resourcePath);
            return getMetadataReader(resource);
        }
        catch (FileNotFoundException ex)
        {
            // Maybe an inner class name using the dot name syntax? Need to use the dollar syntax here...
            // ClassUtils.forName has an equivalent check for resolution into Class references later on.
            int lastDotIndex = className.lastIndexOf('.');
            if (lastDotIndex != -1)
            {
                String innerClassName = className.substring(0, lastDotIndex) + '$' + className.substring(lastDotIndex + 1);
                String innerClassResourcePath = ResourceLoader.CLASSPATH_URL_PREFIX + ClassUtils.convertClassNameToResourcePath(
                        innerClassName) + ClassUtils.CLASS_FILE_SUFFIX;
                Resource innerClassResource = this.resourceLoader.getResource(innerClassResourcePath);
                if (innerClassResource.exists())
                {
                    return getMetadataReader(innerClassResource);
                }
            }
            throw ex;
        }
    }

    @Override
    public MetadataReader getMetadataReader(Resource resource) throws IOException
    {
        return new SimpleMetadataReader(resource, this.resourceLoader.getClassLoader());
    }

}
